The present invention relates to a system for testing the softness of paper.
A number of techniques have been employed in the past for testing the softness of paper and similar materials.
One such technique is disclosed in U.S. Pat. No. 3,683,681 issued Aug. 15, 1972 to R. E. Taylor. In that patent, paper is bent around a plurality of rods. This in turn causes the fibers in the paper to rub against each other and produce an ultrasonic signal. The level of this fiber generated signal is stated to be proportional to the roughness and other factors relating to the softness of the fibers. Specifically, a softer paper is alleged to produce a lower output signal level than will a harder paper. This signal is received by a microphone, amplified, and converted to an audible frequency signal.
U.S. Pat. No. 2,922,303 issued Jan. 26, 1980 to P. S. Veneklasen et al discloses a testing instrument wherein the hand of a textile, or the various properties which may affect the hand, are tested by rubbing a fixed sample of the fabric with a movable sample fabric. According to the patent, the vibration of fibrous elements during frictional engagement between the textile samples is converted to sound by impressing the vibrations through a diaphragm on a cavity. The variations in pressure (or sound) within the cavity are converted by a microphone into an electrical signal.